Typical Of Rivers And Lakes In Beijing Renewable Water Replenishment Ecological Environment Effects

Supplying urban rivers and lakes with reclaimed water is recognized as a superior way for ecological restoration and reconstruction. However, tremendous supplement of reclaimed water will bring intense influence to water quality and quantity. Simultaneously, intensive human activities remarkablely influence urban hydrology, water environment and environmental system, such as changes of biology characteristics. We select typical rivers (Qing river, Beixiao river, Ba river, Tonghui river) and a lake (Olympic Park) supplied by recycled water in Beijing as our study areas. The spatial and temporal variations of water quality are investigated through field work; the influence mechanism of social development and environmental change on water environment are researched combined with a variety of surface environmental information. Based on the comprehensive analysis of water quality characteristics and environmental background, we study the characteristics of reclaimed water and vegetation, and thus establish the eco-environment response models to reveal the interaction mechanisms between recycled water and ecological environment. The environment recovery countermeasures for rivers and lakes using reclaimed water in Beijing are proposed in this study. The conclusions are demonstrated as follows:1) Water resource shortages and backward construction of sewage treatment facilities are important reasons for water environment deterioration in Beijing. It can be seen the best water quality of rivers and lakes supplied by reclaimed water in2008; The water quality have been significant improved from2005; the construction of the sewage/water recycling plants is of great importance to water environment amelioration.2) The rivers are all heavily polluted (inferior Class â…¤ of Environmental quality standards for surface water). The main indicator exceeding the criterion is total nitrogen (TN), which is the primary factor leading to the deterioration of water quality. The water quality of Beixiao river is distinctly worse than the other three rivers, while Tonghui river possesses the best water quality. There is an evident correlation between water quality and seasons except TN and NO2--N. Spatial autocorrelation of water quality indicators is weak, which means they are subject to human activities. The reclaimed water drainage has a distinct effect on reducing COD and NH4+-N content. Majority of water quality values from outfalls in the rivers except for Beixiao river are relatively lower than or basically coincident to that in the up streams. The water quality could be obviously advanced when supplying recycled water to rivers. The nitrogen, organic matter, phosphorus and salinity content, together with uncertainty factors, severely affect the water quality of rivers supplemented by reclaimed water. The water quality in the study is depicted by complex components, high concentrations and intensive anthropogenic interference. The water quality of the recycled water in Olympic Park is much better in comparison with the reclaimed water supplied rivers. However, some indicators, such as TN, TP, beyond the surface water environmental quality standards Grade â…¢. Various water quality data show obvious seasonal variations. Water quality of recycled water is improved significantly after the reclaimed water interacts with the wetland vegetation and microorganisms in the water treatment area and circular lake handling area. Nevertheless, it is still in a moderate eutrophication.3) The environmental background factors influencing reclaimed water quality in rivers involve land use, impervious surface coverage, floodgates and dams, river vulcanized and so on. Most of the water quality indicators (COD, TP, TN and N02--N) exhibited stronger relationship with environmental background factors in the near-shore scale compared with far-shore scale. Considering the spatial impact can enhance the comprehension of the spatial characteristics of water quality.4) The physical and chemical parameters of reed(Phragmites australis) and cattail (Typha angustifolia), including chlorophyll content, ground fresh biomass, total nitrogen content, and total phosphorus content, denote distinct seasonal variations. The seasonal differences of nitrogen and phosphorus content are due to allocation and transport of nitrogen, phosphorus in various organs. Most high values of the physical and chemical indicators of Phragmites australis and Typha angustifolia appear in the circular water treatment area. Phragmites australis and Typha angustifolia biomass are increased by higher nutrition availability in the water, and the overall correlation between nitrogen, phosphorus content of the two species and nutrition in water is obvious. Phragmites australis and Typha angustifolia play an important role in removal of nitrogen and phosphorus. The canopy reflectance of Phragmites australis or Typha angustifolia changes with seasons or coverage. The difference of Phragmites australis or Typha angustifolia reflectance is distinct among reclaimed water treatment areas. The research establishes univariate models involving simple ratio spectral index (SR) model and normalized difference spectral index (ND) model, as well as multivariate models including stepwise multiple linear regression (SMLR) model and partial least squares regression (PLSR) model using the reflectance of Phragmites australis and Typha angustifolia to predict the TN in water and leaves. Moreover, the accuracy of all the models was tested through cross-validated coefficient of determination (R2cv) and cross-validated root mean square error (RMSEcv). The results showed that compared different types of wetland plants, the accuracy of all established prediction models using Phragmites australis reflectance spectra was higher than that using Typha angustifolia reflectance spectra. Compared with univariate techniques, multivariate regressions improved the estimation of TN concentration in water and leaves. Among the various investigated models, the accuracy of PLSR model was the highest. Other environmental factors should also be discreetly considered in modeling exercise.5) Phragmites australis are used to conduct the control experiment. The nitrogen treatment are0,1,2,5,20mg/L. Height, chlorophyll content, biomass, and N concentration of Phragmites australis all illustrate a rising trend with increasing N concentration. The increase of available N promotes the biomass accumulation for each organ. N concentration in root and leaf display a positive relationship. Reflect spectra and1st spectra of Phragmites australis across five fertilization levels have evident performance in the visible and red edge regions; the differences of the reflectance show the effect of N treatment concentration. PRI and CI are most optimal indices to establish the relation between Phragmites australis spectra and N treatment levels, also the relationship between Phragmites australis spectra and chlorophyll content.According to the results mentioned above, we propose that:speed up the construction of recycled water treatment plants, increase the reuse of wastewater reclamation, decrease the negative influence of human beings, establish a favorable plant water purification system, make full use of remote sensing to strengthen monitoring and management are effective ways to restore ecological environment of reclaimed water replenishment rivers and lakes in Beijing. The research results from this study can provide a strong scientific basis for monitoring, management and ecological recovery of lakes and rivers using recycled water.